1. Field of the Invention
This invention relates to a flash photographing apparatus, and more particularly to an improvement on an electronic flash device of the kind arranged to stop a flash tube from flashing when the integrated value of a reflection light from an object to be photographed reaches a predetermined value.
2. Description of the Prior Art
The flashing operation of the conventional devices of the above-stated kind has an extremely steep rising characteristic before it reaches a peak value as represented by FIG. 5 of the accompanying drawings. Therefore, in the event of an electrical delay, which takes place at a light controlling circuit or light quantity limiting circuit or the like during a photographing operation on an object located at a short distance, it has been impossible to obtain an adequate exposure as the flashing stopping time delays due to the electrical delay. In other words, in the case of photographing at a near distance, the flashing operation must be stopped at some point within the steep rise part A. For example, if the flashing operation must be stopped at the point indicated by a broken line "a" in FIG. 5, a time delay "t" takes place to come to another point "al" as indicated by another broken line. This deviation results in an over-exposure. Further, in the case of photographing at distances other than near distances, the flashing operation is stopped at some point on a moderate fall curve B. In that case, therefore, occurrence of the time delay "t" brings about no serious influence on the exposure, as indicated by broken lines "b" and "bl" in FIG. 5. To solve the problem brought about by the steep rise A, it has been attempted to moderate the steep rise by connecting an inductance of a large capacity in series with a flash discharge tube. However, since a considerable amount of resistance is generally included in an inductance, the use of an inductance of a large capacity results in an energy loss caused by the resistance component thereof. As a result, the flashing characteristic becomes as shown in FIG. 6. With an inductance of a large capacity connected, therefore, light quantity becomes insufficient for photographing at a far distance.